Furnace emits a burning dust smell when starting after a long period of inactivity.

Safety: Ensure good ventilation when first starting the furnace after a long shutdown.

Steps:

• Pre-season cleaning: With power off, remove the access panel and gently vacuum dust from the heat exchanger surfaces, fan housing, and cabinet interior.
• Run the furnace: Turn on the furnace and allow it to run for 20–30 minutes with some windows slightly open to clear the smell.

When to worry: If the smell is strong, acrid, or accompanied by smoke, turn off the furnace and call a technician to check for electrical overheating or flue gas leaks.